Circuit interrupters are electrical components that are used to open an electrical circuit, interrupting the flow of current. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed, meaning that the contacts are in electrical contact with each other allowing electricity to flow between them, or open, meaning that the contacts are not in electrical contact with each other preventing the flow of electricity. A switch may be directly manipulated to provide a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Another example of a circuit interrupter is a circuit breaker. A circuit breaker may be used, for example, in an electrical panel to limit the amount of current flowing through the electrical wiring. A circuit breaker is designed to protect an electrical circuit from damage caused by, for example, an overload, a ground fault or a short circuit. If a fault condition, such as, a power surge occurs in the electrical wiring, the breaker will trip. This will cause a breaker that was in an “on” position to flip to an “off” position and interrupt the flow of electrical power through the breaker. Circuit breakers are generally provided to protect the electrical wiring by limiting the amount of current transmitted through the wires to a level that will not damage them. Circuit breakers can also prevent destruction of the devices that may draw too much current.
A standard circuit breaker has a terminal connected to a source of electrical power, such as, a power line electrically connected to the secondary of a power company transformer, and second terminal electrically connected to the wires that the breaker is intended to protect. Conventionally, these terminals are referred to as the “line” and “load” respectively. The line is sometimes referred to as the input of the circuit breaker. The load, is sometimes referred to as the output of the circuit breaker, which connects to the electrical circuit and components receiving the electrical power.
A circuit breaker may be used to protect the electrical wiring that feeds an individual device, or a number of various devices. For example, an individual protected device, such as a single air conditioner, may be directly connected to a circuit breaker. Alternatively, circuit breaker may also be used to protect the wiring feeding multiple devices that may be connected to the circuit via various electrical outlets (e.g., various devices in a room each plugged into an outlet all on the same circuit).
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse however, which typically operates to open in an over current situation once and then must be replaced; a circuit breaker can be “reset” (either manually or automatically) to resume operation. Fuses perform a similar role to circuit breakers, however, circuit breakers are easier to use and typically safer to service and operate.
In a situation where a fuse blows (open) thereby interrupting power to a circuit, it may not be apparent which of the multiple fuses in the panel, feeds the interrupted circuit. Typically, all of the fuses in the electrical panel would need to be inspected to determine which fuse is burned or spent. This fuse would then need to be removed and a new fuse installed.
Alternatively, in the situation where a circuit breaker trips, it is apparent which circuit breaker feeds the interrupted circuit by simply looking at the electrical panel and noting the breaker has tripped to the “off” position. This breaker can then be simply flipped to the “on” position and power will resume.
In general, a single pole circuit interrupter has two contacts positioned inside of a housing. The first contact is stationary and may be connected to either the line or the load. The second contact is movable with respect to the first contact, such that when the circuit breaker is in the “off” or tripped position, a gap exists between the first and second contact.
A problem with the above-described circuit interrupters arises when energized contacts are opened while under load. As the contacts separate transitioning from a closed to an open position, or when the opposition occurs, when the close transitioning from an open to a closed position, an electric arc may be formed in the gap. Arcs are caused when the breakdown voltage between the contacts is positively related to distance under pressure and voltage conditions in typical applications.
The creation of an arc during switching or tripping the circuit interrupter can result in undesirable effects that negatively affect the operation of the circuit interrupter, even potentially creating a safety hazard.
These negative effects can have adverse consequences on the operation of the circuit interrupter.
One possible consequence is that the arc may short to other objects in the circuit interrupter and/or to surrounding objects, causing damage and presenting a potential fire or safety hazard.
Another consequence of arcing is that the arc energy damages the contacts, causing some material to escape into the air as fine particulate matter. The debris which has been melted off of the contacts can migrate or be flung into the mechanism of the circuit interrupter, destroying the mechanism or reducing its operational lifespan.
Another effect of arcing stems from the extremely high temperature of the arc (tens of thousands of degrees Celsius), which can impact the surrounding gas molecules creating ozone, carbon monoxide, and other dangerous compounds. The arc can also ionize surrounding gasses, potentially creating alternate conduction paths.
Because of these detrimental effects it is very important to quickly cool and quench the arc to prevent damage to the circuit interrupter and the above-described dangerous situations.
Various techniques for improved arc quenching are known. For example, U.S. Published Patent Applications No. 2012/0037598 and 2012/0261382, assigned to Carling Technologies, Inc., variously relate to the use of an electromagnetic field to guide an arc toward an arc splitter.
However, generating an electromagnetic field to move an arc requires the use of power, and generates heat in the device. In order to avoid these negative issues, it has been conceived to incorporate a permanent magnet into the circuit interrupter, which produces a magnetic field without requiring a supply of electricity. However, permanent magnets produce a magnetic field having a fixed direction with respect to the magnet. Thus, known solutions for guiding an arc into an arc path using a permanent magnet are circuit polarity dependent. This is due to the fact that an magnetic field produced by a fixed permanent magnet has a fixed direction. As such, the mechanism for magnetically guiding the arc into the path depends upon the direction the current is flowing through the circuit interrupter.
This is a significant limitation, as it prevents such devices from being installed in a circuit where the electrical polarity of the circuit reverses, such as in a typical AC circuit. Hazardous conditions may also arise in a situation where such a device is accidentally installed backwards in that the magnetic field intended to be used to enhance arc quenching will, in fact, operate to drive the arc away from the arc path.
It is therefore desired to provide arc quenching usable with a circuit interrupter that overcomes the above-described limitations.